WHATS THE BEST GRIND; FLAT, HOLLOW OR CHISEL OR,ETC.

Cobalt:

I actually think the tanto is one of the least useful blade shapes, but given that the tanto is what you're interested in, I'll comment no further; let's get on to grinds! You've gone a bit deeper and brought up some good points.

Initially, cutting performance depends on how thin the edge is. It is definitely true that it is possible to grind both a sabre and flat ground blade, and then grind the edges on both to the exact same thickness. At which point, for shallow cutting, you'd expect about the same performance. Of course, it's much easier to *keep* the edge thin on a full flat grind, because the edge bevels thicken so slowly. On a sabre grind, the bevel reaches full spine thickness quickly, and sharpening becomes a chore much quicker.

More importantly, it's worth noting what happens when head out to the yard and start cutting, and chopping. A lot of us who have done hands-on testing have come to the same conclusions -- because the sabre-grind's edge thickens so quickly, it will not penetrate as well (especially deep penetration) as a flat grind. From my testing, the overall rule of edge performance for cutting is: you want the edge and all the metal above it to be AS THIN AS POSSIBLE PROVIDED THE EDGE DOES NOT GET DAMAGED. Flat grinds outperform sabre grinds. Thinner flat grinds outperform thicker flat grinds. As a general rule. Juranitch came to the same conclusions.

You're right that a sabre grind should be a better prybar than a flat grind. However, my main objective for a knife is usually cutting, slicing, chopping, etc. A good flat ground knife can still perform well as a prybar (considering it's a knife and not a prybar), but will outperform the sabre grind in all other aspects.

There are people for whom prybar performance is more important than edge performance, it seems. For them, a chisel grind or thick sabre grind seem like great choices. I just come from the view that for civilians, even for a heavy-duty do-everything knife, edge performance will still be a high priority even if prying needs to be done. You know your own needs better than I do, though, so I can't criticize your choice if it meets your needs. But it's important to point out the edge performance difference in the two grinds.

Joe
jat@cup.hp.com


 
Joe, I cannot disagree with anything you have said, as it is reasonable. I agree that the full flat grind cuts better since it has proven itself many times over the typical saber or modified flay grind. However, I believe that there is a point were a saber grind with the flat ground portion occupying the majority of it's width is nearly as efficient and has the additional strength. To top it off, todays steels are so much better at holding an edge that the difference may be irrelevant. Take a look at a simonich tanto and how the flat ground portion(appears flat ground anyway) is almost 2/3's of the knive's width. I think this is the best tradeoff on a large blade without sacrificing cutting ability.
 
C: Fair enough!

Now, maybe we should start a new thread and have a discussion about the tanto shape and it's strengths and weaknesses for general utility, or whatever it is you have in mind here. It's got so many important weaknesses -- penetration ability, point control, lack of belly -- that I'm thinking you must have something specific in mind for this knife.

Joe
 
Joe in regards to your reply to Ken's post:

The hollow grind Ken is talking about is not like the hollow grind on a Sebenza its more complex and harder to do as the profile is not a constant grind (the cross section has a complicated geometry). You can't file it away as a regular hollow grind, the normal flat/hollow comparasion you state in terms of difficultly doesn't hold.

Second in terms of performance you missed what Ken said. The hollow grind he described combines the best aspects of several grinds. First off it has a thick spine (sabre grind) for prying strength. Second it has a nice edge (convex grind) that is tough for chopping. Third, it has a hollow behind the edge (hollow grind) that produces a low friction enviroment for the material right behind the cut than drags along the knife. This is the reason that the hollow grind cuts well (and the thin edge obviously) as you well know high friction can kill slicing ability.

That type of hollow/convex/sabre grind will give good chopping ability (convex edge), good slicing ability (hollow behind the edge) and still retain decent prying ability (thick spine).

As for hollow grinding axes, well yeah, its not like axes go full depth so its no wonder that you get best performance on a grind optomized for shallow cuts. And of course who does prying with an axe.

As for Ken's rant it looked like an obvious misfire at the other forums and what he describes has happened in the past (not by you).

-Cliff
 
Jim March: Thank you for your comment on by being accurate regarding Japanese swords. However, you made a comment on Mad Dog steel being "vastly better" than something else which I thought I'd take a moment to address.

I believe there may be a misnomer on steel. As I understand it, Mad Dog uses O1 tool steel. In the knife industry, everyone is looking for a "miracle metal" that will cut other metals. This creates a misunderstanding that if Soke Toshishiro Obata can cleave through seven bundles of rolled up mats with a Phill Hartsfield katana, and if that katana is made of A2, then A2 must be a superior steel.

Metallurgically speaking, this is faulty logic. Within martial arts circles, the key to cutting is not the sword but the swordsmanship technique as well as the swordsman. Trained Iaido practitioners could cut even with a slightly blunt sword, believe it or not. So it's more in technique than edge in this case.

However, in terms of what steel is "better" or "the best" you have to consider the right steel for the right tool for the right task.

If you're making Japanese swords then L6, W1, 1084, or 1086 can exceed the performance of traditional Japanese swords, but the requirement is that they are properly thermally treated. There may be tradeoffs, such as L6 will not sport a temper line ('hamon') as clearly as a simpler steel like the AISI 10xx series, but then the other side would be performance.

Tool steels like A2 and O1 are air hardening (I don't recall if O1 specifically is) but in the case for Japanese-style swords, O1 will not take a clay treat as well and will cool even with the clay coat, which basically confounds your ability to differentially harden the steel by traditional Japanese means. You could zone harden steel like A2 with an oxyacetalyne torch, but if you're not consistent, even a steel as "superior" as A2 in this particular application can *crack*.

So I'd conclude by saying that heat treating is far more important than the steel you use. The different metallurgies will give you different properties, responses, requiring different quench mediums, etc. Whatever floats your boat. But take "superior" steel and give it a lousy heat treat and you'll have an *inferior* blade from supposedly superior steel.

This is not said to put down Mad Dog Knives. They may be excellent! But if McClung were to use his techniques and translate them for use of swords, those swords would fail.

[This message has been edited by WarAngel (edited 01 February 1999).]
 
Cliff --

Excuse me if I'm being dense here, but it sounds like what you're describing is just a typical hollow grind, but the final edge is convex ground. Is that right? It's the mid-line (sabre) hollow grind that widens at the bottom that is standard on many Buck fixed blades. I don't remember the edge itself being convex, but I'll take your word for it. Can anyone confirm this?

A couple of notes. The first note being that the edge itself seems to be the most important factor in good cutting -- as you get further back, the thickness is important but becomes less so. For example, David Boye's VERY thick custom blades still outcut nearly everything, because the most important part -- the edge -- is very thin. What I'm getting at is citing the hollow grind behind the edge as a performance increaser is off-target, because the edge on that knife is SO THICK that it performs badly at the edge, before you even get to start worrying about what's going on behind it. Flat bevels or hollow bevels don't matter, because the edge is bad. I've tested this knife, and there have been so many other tests citing terrible edge performance that I feel pretty confident in saying that.

Citing the convex edge as a good feature for chopping I feel is similarly off target, since the format is simply not set up for chopping. The blade is at a zero angle if not slightly negative included angle. Not much weight. Chopping seemed to be an exercise in futility, but if you're going to use it for splitting by banging the spine or otherwise abuse the edge I guess that makes sense. I'd rather have an edge that I could sharpen on standard equipment.

In short, I'll say again that I think the best feature of the hollow grind is its resulting edge thinness. Remove that thinness and the hollow grind loses its appeal. Yes, the fact that the blade remains thin way behind the edge is a nice features, but it can also proveably not make up for a thick bad-performing edge. With this particular grind executed in this way you have a very thick bad-performing edge that is very difficult to sharpen.

Joe
jat@cup.hp.com
 
WarAngel: the only Mad Dog that ever failed was a TUSK that split along a crystalization fault in the original steel from Starret. That's one downside to his game: because he's not personally "re-working" the Starret billets with a heat'n'beat process he's got to "put some trust in" Starret. And they let him down *once*. Kevin made it up to the customer, even though that person had bought the knife *used*.

I've personally chopped through four pine 2x4s and the tip was used to drill through 14 layers of .090 Kydex - with zero affect on the edge or tip. See also Hilton Yam's tests of one of these beasts at www.knifeandtool.com - hit Mad Dog Knives, then the "Torture Test" link.

Jim March
 
Jim March: Kind and gentle sir, I think you missed my point.

A knife that performs well is attributed to heat treating. So if a Mad Dog knife hasn't broken in torture testing, then it can be attributed to the quality of the heat treating process rather than the metallurgy of the steel.
 
I have always thought I preferred flat grinds from my first Case knife to my Gerber
Folding Hunter II that served me faithfully for over 20 years. I have recently waffled a bit
on my stance. I prefer the hollow ground Sebenza for fine detail work and as gentleman’s
steak knife. The flat ground Mad Dog blades do the tough stuff. My favorite daily
complement to the Sebenza being the Pygmy ATAK.

For WarAngel, I don’t know where the myth of not super sharp nihontos came from. My
tired Katana is over 500 years old and is hair popping sharp. The last polish was before
WWII.
 
WarAngel: I hear you, but...sometimes the state a steel is in BEFORE the heat-treat affects the outcome of the heat-treat.

Extreme example: we know about this "in spades" with the high-tech stainlesses like 440C and ATS34. "Burn" 'em while grinding and you've "used up" your one shot at heat-treating...you can send it to the best outside heat-treater in existence and it'll still have weak spots right where you "burned it" before.

This isn't nearly so much the case (if at all) with the simpler high-carbon steels like 1060/1084/1095 series and 5160...but get into "modern tool steels" like A2, 01 and others and it starts to kick in. When Kevin gave his shop tour back in October, he talked about how getting perfectly homogenous billets of Starret 496-01 that had been heated and pounded to absolute uniformity end to end in a multi-ton press was a key to his heat-treat. Yes, 01 is a simple enough steel that it *can* be hand-forged (such as in a Randall) BUT you risk stress fractures at any "uneven pounding points" if you try for the sky-high Rockwells Kevin aims for, a good four to five points above the max hardness of a "heat'n'beat" Randall in 01.

Kevin's point is that if you take a tool steel to the "bitter, ragged edge" of it's hardness and performance envelope, you'd best have "perfect uniformity" before that steel hits the oven...or you better be one DAMN good "pound artist" at the forge. I personally don't doubt that such perfectionists may have existed in old Japan or even somewhere on the planet today - but I think "cold grinding" a factory billet is a lot more likely to produce top results, at least in a tool steel...which is theoretically far tougher stuff than the "simple high carbon" steels related to what the classic Japanese smiths had access to.

Jim March
 
Colin: Traditional Japanese sword edges varied in angle and thickness. You will get some edges that are more convex than others, and some that are sharper than others. In fact, with a good polishing, a Japanese sword could service a family for several generations. If taken care of, you'd probably only need to polish it once in a lifetime. Sharpening and restoration were done in one single action of polishing by a trained Togishi (Japanese sword polisher). My statement about Japanese sword and their sharpness was about sword not needing to be super sharp to do super damage - emphasis is placed in the skill of the swordsman. I said this to address the common "razor sharp" mentality people have when collecting swords. "Razor sharp" also means "razor thin" and an edge that thin in swords is not acceptable on the battlefield, because the sword would be most vulnerable to chipping and other damage.

Jim March: Yes, you'd want to avoid overheating the steel in the grinding process. When I'm at the grinder, I dip the steel into a bucket of water now and then to keep it cool. However, this is only a small measure; the ultimate challenge is the proper heat treating of the sword. Prior to the final quench, you'd want to normalize the steel. Ultimately, annealing the blade will - pardon the pun - "iron out the kinks". Some choose to do this several times to leave no stone unturned.

Tool steel can be "tougher" than steel derived from traditional Japanese iron-bearing sand. But that depends on your definition of "tougher". Metallurgically speaking, "toughness" is related to "softness" which allows for impact absorption and shock tolerance - hence the blade is "tougher." I'm gathering that you're referring to a blade being more "punishable."

However, what works for knifes does not necessarily work for swords. And different metallurgies and alloy mixes will respond differently. On one hand you get your air-hardening tool steels. On another hand, you get your low-alloy high carbon steels that use water as a quenching medium. Tool steels behave differently, have different austenitizing temperatures, cooling rates, etc. Whatever challenges you encounter in knives will be multiplied in longer lengths as swords. As someone recently told me, Kevin McClung was publically recorded as having said that swords are longer knives. I couldn't disagree more.


 
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